amore is used for boy that love a girl, it's a very big and hot passion.
voler bene means affection, attachment, without passion.
the trend is using love like you use to do in USA.
so we use LIKE for something, love for someone,
someone talk about his pets like they are humans, so he uses "love".
amore materno is a big branch, it's mother love, without hot sex passion, but it's stronger that "voler bene".
summarize: amare can have rate of 10/10, amore materno 9/10, voler bene have 8/10, friendship have 7/10, workmates 5/10 ....